Answer:
Explanation:
2Ca is the elemental form of calcium. There are 2 mols of calcium in whatever equation you are talking about.
Ca_2 means that there are 2 ions of Calcium making up something like
Ca3(PO4)2 means that you have the compound Ca3(PO4)2 with 2 mols of PO4 and 3 moles of Ca
It is hard to come up with something composed of Ca2 because unless the other ion is odd, the 2 will divide into something.
